Unauthorized charges in my account

Ordered groceries at special price and paid for it. Scheduled delivery. They changed the process to R117 more. Debited my account again for the second amount without authorization. have a screenshot as proof of the original price charged yet they ignore me and send generic messages that the prices are correct. They refuse to fix it. Now doing the same on my account for my mum. I ordered items for pick up. They did not have one of the items in stock so supposed to refund. Instead they are charging me R97 more. They have no right to debit our accounts for second amounts without authorization. When there's no money in the account, there's charges for the decline. They tried 4 times. Thats 4 charges. Then when I transferred money into the account, they tried again and stole my money. I blocked them. They are *******